How calculate the shape of a target?

Hello Igor,

Could you please be more specific about the application? There are several ways to do it, depending on what exactly you are trying to sense.

Let me give you an example to clarify. If I want to detect linear motion and I have a circular coil, then I would use a target of triangular shape. If I want to detect rotational motion with the same coil, I will need to translate the triangulare shape I mentioned from cartesian coordinates to polar.

For linear position sensing, please refer to the following:

e2e.ti.com/.../inductive-sensing-linear-position-sensing-part-1

e2e.ti.com/.../inductive-sensing-linear-position-sensing-part-2

Best Regards,
Natallia Holubeva

Hello, Natalia,
in the slyb212.pdf examples those triangles are not strait triangles but with somewhat curved sides...
And as about rotational targets - their shape seems to be even more complex. How can the curved triangle
shape be translated into polar coordinates?
Yes, we are trying to measure the angle of rotation of a shaft using the circular coils. Two coils or three - that is
also a question. We need detecting only less then 180 degrees of rotation.
Best wishes,
Igor Gorbounov

Igor,

You can regard it as a triange. The analog wire blog I mentioned in the previous post has data with the target being a triangle.

Coordinate systems are explained wellhere:
en.wikipedia.org/.../Coordinate_system

You can also refer to textbooks of Trigonometry, Calculus, or Electromagnetics. The coordinate systems and ways to translate one to another are covered in multiple textbooks for both ungergraduate and graduate classes.

I am working on incremental rotation design and using IQ modulation for it. What resolution are you trying to achieve? What is the diameter of the shaft?

Best Regards,
Natallia Holubeva

Natalia,
we need to measure a valve actuator position so resolution a little less than degree would be enough. The major criteria here are
reliability, repeatability and low cost.
Best regards,
Igor Gorbounov

Igor,

Thank you for explanation. What is the diameter of the shaft? Will it vary with height? Do you need incremental or absolute sensing?

Best Regards,
Natallia Holubeva

Hm, Natalia,

I'm not quite sure that do undestand what "incremental" or "absolute" sensing means. And in this our new application

the diameter of the shaft does not matter at all. It is about 10 mm in diameter all along and on the end of it a curved-triangle

target should be somehow fixed. Under it (or, maybe, above it) the coils should be placed and then, I hope, the whole thing

will measure the angle of rotation of that shaft.

Thanks for your patience,

      Igor Gorbounov

Hello Igor,

The diameter does matter. Your target and coils should be aligned and the target sets the coil size. Could you please attach a block diagram or a picture of your system?

Incremental position sensing is implemented in the knob of your car radio. When the system is off and you move the knob, it will not affect anything once the system turns back on. Absolute position sensing is needed when you want to detect the angle even if the system has been modified in the OFF mode.

Best Regards,
Natallia Holubeva

Hi, Natalia,
the target is to be fixed perpendicular to the shaft. I'm not sure if I can write down a picture of the thing.

Now I understand the position sensing and it should be an absolute position sensing.

Best regards,
Igor Gorbounov

Hello Igor,

Thats a good start. Do you expect any height variation of the system? If yes, you will be better off waiting until we come up with an algorithm for height compensation. It should take a couple more months.

Best Regards,
Natallia Holubeva

Natalia,
we hope that three coils will help us compensate some variations in system behaviour.

Best wishes,
Igor Gorbounov

Igor,

I assume 1st coil is for in-phase, 2nd for quadrature, and 3rd for compensation. This sounds reasonable.

Best Regards,
Natallia Holubeva

Hello Natalia,
does it mean, that a new kind of a microscheme is to be expected?

Best wishes,
Igor Gorbounov

Igor,

As I understand what you mean by microscheme is the Integrated Circuit (IC). The answer to your questions requires the non-disclosure agreement between your company and TI. You could either contact laywers of your company, your distributor Sales Person or Field Application Engineer.

Best Regards,
Natallia Holubeva

Natalia,

the NDA was signed by our firm (Topaz-Service) in July 2014, although we've seen no sensitive information yet.

I don't need any inner information, just wonder if you were talking about some new method or some new hardware, that is all.

Best wishes,

     Igor Gorbounov

Igor,

Let's start with the method. Do you expect your system to vary with z-axis?

Best Regards,
Natallia Holubeva

Hello Igor,
Please clarify - are you looking for BOTH rotational and Lateral sensing?

Hello TI team,
we do not expect any variation in z-axis, we consider it as an interfering parameter.
And, for the time being, we are working at rotational sensing only.
Best regards,
Igor Gorbounov

Igor,

Thank you very much for clarification. Please, let us know if you have any additional questions. If you have a question about the roadmap or any questions containing confidential information covered under NDA, please send us a private message versus posting it on the public forum.

Best Regards,
Natallia Holubeva